Concrete expansion joints



J. N. HELTZEL CONCRETE EXPANSION JOINTS Feb. 5, 1957 Filed July 23, 1948 INVENTORY /112- M fleli'zel ATTORNEY CONCRETE EXPANSION JOINTS John Nicholas Heltzel, Warren, Ohio; The Union Savings & Trust Company, Warren, Ohio, and Carl J. Heltzel, executors of John N. Heltzel, deceased Application July 23, 1948, Serial No. 40,328

4 Claims. (Cl. 94-18) This invention relates to dowel means for concrete expansion joints, or contraction joints.

The invention is more particularly concerned with improved dowel means for expansion joints as provided between concrete or similar slabs or sections of roadways, floors, airfield runways, walls, and the like, for permitting relative horizontal movement of the slabs, while preventing the same from shifting laterally and vertically of their planes; and the present application is a division of my application Serial No. 553,057, filed September 7, 1944, which in turn is a continuation-inpart of the application filed January 9, 1940, which matured into Patent No. 2,358,328, dated September 19, 1944.

Modern traffic conditions on highways and airfield runways have necessitated an increased use of load transfer members bridging join-ts, both longitudinal or transverse, between the opposed edges of adjacent concrete slabs. Experience has shown that the problem is not solved by the mere addition of load transfer dowels, such as commonly employed, for the shrinkage of plastic concrete when drying sets up a frictional drag on the embedded dowel bars, with the consequent breaking of the concrete at points remote from the joints between the slabs. It has been found, also, that where dowel bars alone are depended upon, there is an inevitable warping of the concrete slabs which tends to bend the dowel bars. This bending prevents restoration of the slabs to their initial condition on the subgrade, and in addition, there is a constant breaking away of concrete or'spalling otf of the material at the faces of the concrete slabs in the areas surrounding and adjacent to the dowel bars.

The tendency of adjacent concrete slabs and the joints between the slabs to shift under changing atmospheric conditions as well as under the incessant loads passing thereover has long been recognized, and the provision of efiicient load transfer means at such joints has attracted the skill of engineers in many fields as well as steel and concrete contractors, and as a result many varieties of load transfer means in the form of dowels bridging con crete slab joints have been proposed and used.

In the use of such load transfer dowels, it is necessary, of course, that expansion and contraction of the joint be permitted, as a result of which the dowels must have relative movement to one of the slabs adjacent a joint in a direction axially of the dowels, and it is also essential that the dowels have relatively no movement trans versely of their axes.

It has been found that dowels in use with concrete expansion joints should, for greatest efiiciency, be so united with at least one of the slabs as to remain rigid therewith under all conditions of use, and that such united dowels be confined to axial movement only relatively to another slab.

It. has also been found that for maximum elliciency the load bearing members or dowel structures should be so constructed and arranged as to be balanced on opposite sides of the joint and that the dowel portions spani d States Patent .s

2,780,149 Patented Feb. 5, 1957 ning the joint should have a maximum load bearing and transferring capacity vertically through the dowel.

It is a primary object of the invention, therefore, to provide dowel means for concrete expansion joints and the like which satisfy the above noted requirements in providing load transfer connections of maximum strength and efficiency.

An object of the present invention, therefore, is to provide improved means for producing joints in concrete roads and the like, utilizing dual dowel means in asso-' ciation with dual supporting shear plates, in which friction with respect to the surrounding concrete is reduced to a minimum by the novel bridging structure of balanced dowel and bearing members.

Another object is to provide, in such joints, means to eliminate tension in the concrete itself and to confine such tension directly and uniformly to the dowel and shear plate means constituting the load transfer elements extending in balanced relation between the respective slabs.

A still further object is to provide a dual dowel assembly concrete slab in a joint installation for transferring vertical load strain to the dowel means at the joint by the employment of cooperating dual shear plates associated with the concrete slabs and dowels.

A further object of the invention is the provision of dowel means for concrete expansion joints including a dowel and dowel shear plate and socket arranged for rigid connection with each slab adjacent a joint therebetween with provision for each dowel to telescopically engage within a socket in the expansion and contraction of the joint.

A still further object of the invention is the provision of a dowel unit for use in concrete expansion joints comprising a pair of shear plates, each having a dowel and dowel socket rigid therewith, each shear plate having an aperture for confining the dowel of the other shear plate to axial movement in expansion or contraction of the connected concrete slabs, and each shear plate having means rigid therewith for transmitting strains remote from the joint directly to the shear plate.

A still further object of the invention is the provision of dowel means of the above noted character, wherein the shear plates are retained for contact with an expansion joint strip during pouring of concrete in the formation of slabs thereof.

A still further object of the invention is the provision of dowel means for concrete expansion joints including elements for cooperation at opposite sides of the joint and which elements are of like construction whereby manufacture and the setting up of the dowel means is simplified to a notable extent.

A still further object of the invention is the provision of dowel means for concrete expansion joints wherein the joint is greatly strengthened and balanced at each side thereof.

With the above and other objects in view, which will become more fully apparent as the nature of the invention is better understood, the same consists in the novel features of construction, combination and arrangement of parts as will be hereinafter more fully described, illustrated and claimed in the accompanying drawings.

In the drawings, wherein like characters of reference denote corresponding parts in related views:

Fig. l is a perspective view showing the separated elements of Fig. 4 in assembled position;

Fig. 2 is a sectional perspective view disclosing a further embodiment of the invention;

Fig. 3 is an enlarged transverse sectional view substantially in the plane of line 3-3 of Fig. 2;

Figure 4 is a sectional perspective view disclosing a further embodiment of the invention.

Referring now in detail to the drawings, and first to Fig. 1, wherein is disclosed a dual dowel reinforcing and load transferring structure for use at the joints of concrete slabs and which structure is also characteristic of the disclosure in Figures 2 and 3.

Referring now to Figure 1, the shear plates 11a are provided with upper and lower flanges 2'5 and 26 for anchorage in the concrete slabs whereby holding the shear plates effectively in position. Their upper flanges 25 are preferably provided with openings 27 to permit concrete to flow about the structure and honey-combing of the plastic material. The openings 27 further function to more firmly unite the flanges with the concrete. The bar portions 15a in this embodiment are provided with laterally deflected rear end portions 28 for the purpose of greater anchorage in the concrete body of a slab as well as stress-relieving.

In this embodiment of the invention the bar portions 15a are provided with openings 29 for receiving a temporary wire shear plate support 30. The support may comprise opposed portions 31, each having a linear subgrade engaging portion provided with an angle portion 32 to permit contraction and expansion of the slabs. The support is primarily adapted to maintain the structure above the sub-grade and when it is desired to elevate the structure to a higher position, the portions 31 are brought closer and when it is desired to lower the structure, the portions 31 are spread apart. In this manner the assembly may be supported in a variable position above the sub-grade.

A further embodiment of the invention is illustrated in Figs. 2, 3 and 4 which show the same general organization as previously described. The shear plates 11b are provided with upper and lower right angular flanges 35 and 36, respectively, and the upper flanges 35 are each provided with an aperture 37. In this embodiment the usual expansion joint strip 22 is supported or held with its openings 23 in registration with the aperture 12 by a removable cap strip 38 which is of inverted U-shape. This cap strip as shown is provided with prongs 39 in registry with the apertures 37 and for entering same as indicated. This also temporarily prevents separation of the shear plates from the strip 22 after setting up of the parts.

In this embodiment the bar portions 1512 are provided with downwardly projecting supports 40 for engagement with the sub-grade. Such supports are of a length to support the joint strip 22 on the sub-grade, or if desired in a suspended position. The cap strip 38 is removed prior to the final finishing of the concrete slabs. A wire spring member 41 may extend between the supports 40 to aid in holding the shear plates against the joint strip. However, when the cap strip 38 is used, such spring member may be omitted. The bar portions 15b may further be provided with upwardly diverted anchorage portions 4-2 for better uniting the bars with the concrete slabs.

As will be appreciated the top and bottom flanges 35, 36, of the shear plates 11!) constitute top and bottom shear plate reinforcing means to resist stresses tending to bend the plates along lines extending from the top to the bottom thereof. Likewise the dowels 15a, 15b of Figures and 8, respectively, being functionally integral with the related shear plates 11a, 11b reinforce such plates at the mid-portions thereof and operate to resist distortion of same at the site of the openings or apertures therein through which the dowel of the coinpanion plate extends when the units are assembled.

While several embodiments of the invention are herein disclosed, it is to be particularly noted that the same general principle is common to all. The modifications are in fact only illustrative of the different forms that the shear plates may take, as Well as the relationship of the dowels to each other, the means for preventing separation of the shear plates and dowels during pouring of concrete in the formation of slabs, and means for firmly bonding the elements with the concrete and for transmitting strains from points distant from the plates or expansion joint to the plates with which the dowels are rigidly connected.

In all of the embodiments disclosed, however, each load transmitting unit comprises a pair of shear plates to be embedded in adjacent end faces of the concrete slabs as is clearly shown in Fig. 3, and each shear plate has rigidly connected therewith and extending therethrough a bar member, a porton of which provides a dowel and another and longer portion provides for firmly bonding the shear plates with the slab and for transmitting strains from points distant from the joint to the shear plates.

Thus it will be observed that the shear plates, when embedded in and firmly bonded with the slabs as disclosed, there is no tendency or even possibility of the dowels having any movement transverse of their axes relative to the slabs with which they are united. Furthermore, the novel structure is such that in use the dowels cannot have lateral movement independently of each other or with the slabs with which they are relatively lengthwise movable, for the reason that the dowel-receiving apertures in the various shear plates are of a vertical dimension so as to provide a close sliding lit with the upper and lower edges of the dowels.

Thus, upon consideration of Figs. 1, 2 and 4, it will be noted that each dowel 16 is rigidly supported by the shear plate in one slab S and is confined by the aperture 12 in the opposed shear plate 11 to horizontal or axial movement. Thus, the two dowels 16 provide a rigid load transmitting truss between the opposed edges of the slabs S.

In both forms disclosed, the bars and dowels have substantial vertical depth for maximum load transmitting properties and such bars and dowels are disposed substantially distant from the top surface of the slabs so as to avoid an otherwise possibility of cracking thereof.

Each unit in each embodiment of the structure disclosed comprises a pair of substantially identical members, which not only simplifies manufacture but also materially expedites assembly in that it is not necessary to select left and right members, as is the case with prior structures of this general character. Furthermore, the member are relatively simple in construction and can all be formed from bar and sheet material.

From the above description, it is believed that the features and advantages of the invention will be readily apparent to those skilled in the art, and it will, of course, be understood that changes in the form, proportion and minor details of construction may be resorted to without departing from the spirit of the invention and scope of the appended claims.

Having thus described my invention, what I claim is:

1. Load transfer means for concrete expansion joints comprising a pair of relatively movable shear plates for operative disposition on opposed sides of an apertured expansion strip in the joint, a dowel member projecting through and secured to and functionally integral with each shear plate and extending from opposite sides thereof, an aperture in each plate for receiving the end of the dowel extending from the opposed plate, a shear plate bracing support depending from the other end of each dowel for holding the opposed shear plates in engagement with the opposite sides of the expansion strip, a dowel-receiving socket rigid with the slab side of each shear plate about said plate aperture and said shear plate bracing support comprising a pair of opposed and oppositely spreadable props in the form of subgrade-supported U-shaped rods, and adjacent ends of the respective rods pivotally secured to said other end of the adjacent dowel.

2. Load transfer means for concrete expansion joints comprising a pair of relatively movable shear plates for operative disposition on opposed sides of an apertured expansion strip in the joint, a dowel member pnojecting through and secured to and functionally integral with each shear plate and extending from oppositesides thereof, an aperture in each plate for receiving the end of the dowel extending from the opposed plate, a shear plate bracing support depending from the other end of each dowel for holding the opposed shear plates in engagement with the opposite sides of the expansion strip, a dowel-receiving socket rigid with the slab side of each shear plate about said plate aperture, and said shear platebracing support comprising a pair of opposed and oppositely spreadable props which are subgrade supported at their outer ends, the inner ends of said props pivotally secured to said other end of the adjacent dowel whereby to support the dowel members and shear plates different distances above the subgrade.

3. Load transfer means for concrete expansion joints comprising a pair of relatively movable shear plates for operative disposition on opposed sides of an apertured expansion strip in the joint, a dowel member projecting through and secured to and functionally integral with each shear plate and extending from opposite sides thereof, an aperture in each plate for receiving the end of the dowel extending from the opposed plate, a shear plate bracing support depending from the other end of each dowel for holding the [opposed shear plates in engagement with the opposite sides of the expansion strip, a dowelreceiving socket rigid with the slab side of each shear plate about said plate aperture, and said shear plate bracing support comprising a pair of opposed and oppositely spreadable props in the fiorm of subgrade-supported U-shaped rods, adjacent ends of the respective rods pivotally secured to said other end of the adjacent dowel whereby the shear plates and dowels can be supported different distances above the subgrade, and the bight portions of each of said U-shaped rods having an ofiset at the site of said joint whereby to permit contraction and expansion of the slabs when formed.

4. Load transfer means for concrete expansion joints comprising a pair of relatively movable shear plates for operative disposition on opposed sides of an apertured expansion strip in the joint, a dowel member projecting through and secured to and functionally integral with each shear plate and extending from opposite sides thereof, an aperture in each plate for receiving the end of the dowel extending from the opposed plate, a shear plate bracing support depending from the other end of each dowel for holding the opposed shear plates in engagement with the opposite sides of the expansion strip, a dowel-receiving socket rigid with the slab side of each shear plate about said plate aperture, and said shear plate-bracing support comprising a pair of opposed and oppositely spreadable props in the form of subgrade-supported U-shaped rods, adjacent ends of the respective rods pivzotally secured to said other end of the adjacent dowel whereby the shear plates and dowels can be supported dilferent distances above the subgrade, and the bight portions of said U-shaped rods being offset at the site of said joint whereby to permit contraction and expansion of the slabs when formed, and the last mentioned ends :of said dowels having slab-embedded anchors whereby to counteract any tendency of said U-shaped rods to prevent separation of said shear plates as the slabs in which they are embedded contract.

References Cited in the file of this patent UNITED STATES PATENTS 1,121,303 Robertson June 21, 1938 2,179,911 Wilmoth Nov. 14, 1939 2,201,134 Brickman et al May 21, 1940 2,261,602 Yeoman Nov. 4, 1941 2,267,023 Godwin Dec. 23, 1941 2,296,756 Yeoman Sept. 22, 1942 2,319,713 Williams May 18, 1943 2,325,472 Brickman July 27, 1943 2,365,550 Heltzel Dec. 19, 1944 2,416,584 Heltzel Feb. 25, 1947 

